Effects of angiotensin II AT1 receptor inhibition and exercise training on insulin action in rats on high-fat diet

AimThis study was to determine whether combination of the angiotensin II AT1 receptor blocker (ARB), candesartan cilexetil, and exercise training can prevent the development of high-fat diet-induced insulin resistance.Main methodsF344/NSlc rats were fed normal chow diet or high-fat (HF) diet for 7 weeks. The HF-fed rats were either administered candesartan cilexetil (5 mg·kg^? 1·day^? 1), exercise-trained, or received a combination of these 2 treatments.Key findingsOral glucose tolerance tests (OGTT) showed that combined treatment with candesartan cilexetil and exercise increased glucose tolerance as compared with each treatment alone in HF-fed rats. Moreover, euglycemic–hyperinsulinemic clamp analysis showed improvement in glucose infusion rate with exercise training or candesartan cilexetil treatment alone, and further improvement was observed with the combination treatment. Systolic blood pressure improved with candesartan cilexetil but not with exercise alone. Finally, Glut-4 protein expression in soleus muscle was decreased with HF diet, and the expression was increased by exercise and not candesartan cilexetil treatment.SignificanceThese results suggest that the combination of candesartan cilexetil and exercise training improves insulin resistance as compared with each treatment alone.     

坎地沙坦酯治疗老年患者原发性高血压的疗效及安全性分析

目的:探讨坎地沙坦酯治疗老年高血压患者的疗效和安全性。方法:选取我院110例老年原发性高血压患者,随机分为观察组(坎地沙坦酯治疗)和对照组(依那普利治疗),对比分析两组患者药物治疗前、后的动态血压监测及相关指标。结果:经两个月治疗后,两组患者坐位收缩压(SBP)及舒张压(DBP)谷值均较基线明显降低,观察组下降幅度明显大于对照组,差异有统计学意义(P0.05);观察组的总有效率为90.91%,明显高于对照组的76.36%,差异有统计学意义(P0.05)。结论:坎地沙坦酯治疗老年患者原发性高血压疗效显著,可明显降低收缩压和舒张压,是治疗老年性高血压理想的制剂。     

Possible role of VEGF in the progression of kidney disease in streptozotocin (STZ)-induced diabetic rats: effects of an ACE inhibitor and an angiotensin II receptor antagonist.

Two endothelium-derived factors, endothelin (ET), a vasoconstrictor, and vascular endothelial growth factor (VEGF), an angiogenic factor are thought to be involved in the pathogenesis of diabetic vascular complications. The aim of this study was to determine the effects of an angiotensin II type I (AT-1) receptor antagonist and an ACE inhibitor on the pathogenesis of VEGF and ET-1-mediated kidney disease in STZ-induced diabetic rats. Two days after STZ administration, diabetic rats were treated for 8 weeks with enalapril maleate, an ACE inhibitor, candesartan cilexetil, an AT-1 receptor antagonist, or saline. Urinary albumin and N-acetyl beta-D glucosaminidase (NAG) excretion as well as the VEGF protein content in the kidney were all found to be elevated in diabetic rats. Administration of enalapril maleate or candesartan cilexetil decreased the level of microalbuminuria and NAG excretion in diabetic rats. Administration of enalapril maleate also suppressed the elevated renal VEGF protein content in these animals while candesartan cilexetil treatment had no effect. Serum ET-1 and VEGF levels were unchanged by these treatments. These data support a role for AT-1 receptor antagonists and ACE inhibitors in the prevention of diabetic nephropathy, and suggest that the former may work by reducing renal VEGF levels.     

Acute treatment with candesartan cilexetil, an angiotensin II type 1 receptor blocker, improves insulin sensitivity in high-fructose-diet-fed rats

We aimed to determine whether acute treatment with candesartan cilexetil (CV-11974), an angiotensin II type 1 receptor blocker (ARB) can improve insulin sensitivity in high-fructose-diet (HFD)-fed rats. In vivo glucose utilization was measured by applying the euglycemic clamp technique and the expression levels of insulin-signaling molecules in skeletal muscles were examined by western blotting. A bolus injection of CV-11974 improved the glucose infusion rate (GIR) of HFD-fed rats to the level of the control rats. Furthermore, restoration of impaired tyrosine phosphorylation of insulin receptor (IR) β, Akt phosphorylation at Ser??3 and Thr3??, and phosphorylation of the 160-kDa Akt substrate (AS160) in the skeletal muscles of HFD-fed rats were achieved by this treatment. These results suggest that acute administration of candesartan cilexetil can increase insulin sensitivity of HFD-fed rats, which is associated with improved insulin signaling in skeletal muscles.     

Solid Self-Microemulsifying Formulation for Candesartan Cilexetil

Sparingly, water-soluble drugs such as candesartan cilexetil offer challenges in developing a drug product with adequate bioavailability. The objective of the present study was to develop and characterize self-microemulsifying drug delivery system (SMEDDS) of candesartan cilexetil for filling into hard gelatin capsules. Solubility of candesartan cilexetil was evaluated in various nonaqueous careers that included oils, surfactants, and cosurfactants. Pseudoternary phase diagrams were constructed to identify the self-microemulsification region. Four self-microemulsifying formulations were prepared using mixtures of oils, surfactants, and cosurfactants in various proportions. The self-microemulsification properties, droplet size, and zeta potential of these formulations were studied upon dilution with water. The optimized liquid SMEDDS formulation was converted into free flowing powder by adsorbing onto a solid carrier for encapsulation. The dissolution characteristics of solid intermediates of SMEDDS filled into hard gelatin capsules was investigated and compared with liquid formulation and commercial formulation to ascertain the impact on self-emulsifying properties following conversion. The results indicated that solid intermediates showed comparable rate and extent of drug dissolution in a discriminating dissolution medium as liquid SMEDDS indicating that the self-emulsifying properties of SMEDDS were unaffected following conversion. Also, the rate and extent of drug dissolution for solid intermediates was significantly higher than commercial tablet formulation. The results from this study demonstrate the potential use of SMEDDS as a means of improving solubility, dissolution, and concomitantly the bioavailability.     

Effect of an ACE inhibitor and an AT1 receptor antagonist on cardiac hypertrophy

The effect of long-term administration of delapril, an angiotensin converting enzyme inhibitor, and candesartan, an angiotensin II receptor blocker, on cardiac hypertrophy was investigated in spontaneously hypertensive rats (SHR). Delapril (2 mg/kg/day) and candesartan (2 mg/kg/day) were administered for 5 weeks to 15-week-old male SHR. Echocardiographic estimation of cardiac morphology and function revealed cardiac hypertrophy in SHR compared with Wistar-Kyoto rats (WKY) which were used as normal controls. Both treated groups revealed regression of cardiac hypertrophy estimated by echocardiography. Heart to body weight ratio of treated SHR was also smaller than that of untreated SHR. Plasma BNP and ANP concentrations were increased in untreated SHR and decreased in the treated groups. Histological examination was performed using light microscopy and the area of fibrosis was estimated by computer. Reduction of the fibrotic area was observed in SHR treated with delapril and candesartan, although the latter was not statistically significant. Immunohistochemical examination using anti-collagen monoclonal antibody showed a decrease of type I collagen in treated SHR as compared with untreated SHR. It is concluded that both angiotensin converting enzyme inhibitor and angiotensin II receptor blocker sufficiently reduce blood pressure in SHR associated with regression of cardiac remodeling.     

Determination of candesartan cilexetil, candesartan and a metabolite in human plasma and urine by liquid chromatography and fluorometric detection

Liquid chromatographic methods are described for the determination of a new effective anti-hypertensive drug candesartan (CV-11974), its prodrug candesartan cilexetil (TCV-116) and a metabolite, CV-15959 in human plasma and urine. The assays comprise liquid–liquid extraction and separation on a phenyl column with fluorometric detection. The methods give absolute recoveries of 70, 83 and 78% for candesartan cilexetil, candesartan and CV-15959, respectively, and the limit of quantification is 5, 1 and 3 nM of plasma (RSD<20%), respectively. The methods were applied to plasma and urine samples from biopharmaceutical and clinical studies in man.     

Interaction of angiotensin II type 1 receptor blockers with P-gp substrates in Caco-2 cells and hMDR1-expressing membranes

AimsThe inhibitory effect of angiotensin II type 1 receptor blockers (ARBs) on P-glycoprotein (P-gp) was examined to evaluate their clinical drug–drug interaction (DDI) potential.Main methodsWe performed an inhibition study on the vectorial transport of digoxin, a typical substrate for P-gp, using a human colonic adenocarcinoma cell line, Caco-2 cells, and verapamil-stimulated ATPase activity using human multidrug resistance 1 (hMDR1)-expressing membrane.Key findingsThe vectorial transport of digoxin was inhibited by candesartan cilexetil, irbesartan and telmisartan with the IC₅₀ values of 14.7, 34.0 and 2.19 µM, respectively. Those values were 7.4–426-fold higher than their theoretical clinical gastrointestinal concentration [I] at doses in clinical DDI studies. Other ARBs failed to show interaction with P-gp.SignificanceIt was demonstrated that candesartan cilexetil, irbesartan and telmisartan had the potential to inhibit the transport of various drugs via P-gp. Telmisartan, which caused an increase in the serum digoxin concentration in humans, had a sufficiently high [I]/IC₅₀ value, suggesting that DDI between digoxin and telmisartan was caused by the inhibition of digoxin efflux via intestinal P-gp.     

Differential effects of losartan and candesartan on vasoconstrictor responses in the rat

Losartan has been reported to have inhibitory effects on thromboxane (TP) receptor-mediated responses. In the present study, the effects of 2 nonpeptide angiotensin II (AT1) receptor antagonists, losartan and candesartan, on responses to angiotensin II, the thromboxane A2 mimic, U46619, and norepinephrine were investigated and compared in the pulmonary and systemic vascular beds of the intact-chest rat. In this study, intravenous injections of angiotensin II, U46619, and norepinephrine produced dose-related increases in pulmonary and systemic arterial pressure. Losartan and candesartan, in the doses studied, decreased or abolished responses to angiotensin II. Losartan, but not candesartan, and only in a higher dose, produced small, but statistically significant, reductions in pressor responses to U46619 and to norepinephrine in the pulmonary and systemic vascular beds. Furthermore, losartan significantly reduced arachidonic acid-induced platelet aggregation, whereas candesartan had no effect. Pressor responses to angiotensin II were not changed by thromboxane and alpha-adrenergic receptor antagonists, or by cyclooxygenase and NO synthase inhibitors. These results show that losartan and candesartan are potent selective AT1 receptor antagonists in the pulmonary and systemic vascular beds and that losartan can attenuate thromboxane and alpha-adrenergic responses when administered at a high dose, whereas candesartan in the highest dose studied had no effect on responses to U46619 or to norepinephrine. The present data show that the effects of losartan and candesartan on vasoconstrictor responses are different and that pulmonary and systemic pressor responses to angiotensin II are not modulated or mediated by the release of cyclooxygenase products, activation of TP receptors, or the release of NO in the anesthetized rat.     

Development and Characterization of Mixed Niosomes for Oral Delivery Using Candesartan Cilexetil as a Model Poorly Water-Soluble Drug

The aim of this study was to prepare candesartan cilexetil-loaded niosomes and mixed niosomes to enhance the aqueous solubility of the drug, thus improving its oral bioavailability. The formulations were prepared using various types and combinations of surfactants, copolymers, and charge-inducing agents. The candesartan cilexetil entrapment efficiency, particle size, and zeta potential of these niosomes varied within the range of 99.06 ± 1.74 to 36.26 ± 2.78, 157.3 ± 3.3 to 658.3 ± 12.7 nm, and −14.7 ± 2.8 to −44.5 ± 1.5 mV, respectively. The in vitro drug release from niosomes was improved after niosomal entrapment compared to pure candesartan cilexetil. The sedimentation behavior study and formulation stability tests against bile salt revealed that mixed niosomes prepared by combining Span 60 and Pluronic P85 demonstrated better stability. The differential scanning calorimetry analysis showed the conversion of crystal structure of candesartan cilexetil to the soluble amorphous form after niosomal encapsulation which induced the drug release. Consequently, oral drug delivery by Span 60/Pluronic P85-mixed niosomes seems feasible due to enhanced drug release and stability.KEY WORDS: in vitro drug release, niosomes, oral drug delivery, stability, surfactants     

The Effect of Polysorbate 20 on Solubility and Stability of Candesartan Cilexetil in Dissolution Media

The addition of polysorbate 20 (T20) is required to achieve “sink” conditions during a dissolution test for tablets with candesartan cilexetil (CC). Polysorbate 20 (0.35%–0.7% w/w) added to 0.05 mol/L of phosphate buffer pH 6.5 dramatically increased the apparent solubility of the drug from 0.8 μg/ml even to 353 μg/ml, while its effect in lower pH or in water was much smaller (20 μg/ml in pH 4.5). The increased concentration of phosphate salts (0.2 mol/l) at pH 6.5 in the presence of 0.7% of polysorbate 20, resulted in further increase of candesartan cilexetil solubility to 620 μg/ml. The change of pH from 1.2 to 7.4 resulted in a 1.5-fold increase of the activation energy and, depending on temperature, 8–14-fold decrease of the degradation rate. When polysorbate 20 increased the activation energy 2-fold, independent of pH, it protected candesartan cilexetil from degradation; however, this effect was temperature dependent and was very small at 310 K—the degradation rate in pH 6.5 decreased by 13% only. It was calculated that in the phosphate buffer pH 6.5 with polysorbate, one can expect during 24 h the degradation at the level of 9.3%, thus a flow-through dissolution apparatus was recommended for testing prolonged release dosage forms.     

Effect of angiotensin II type 1 receptor antagonist on tumor growth and angiogenesis in a xenograft model of human bladder cancer

Several authors have investigated the antitumor activity of angiotensin II type 1 receptor (AT1R) antagonists, which are widely used as antihypertensive drugs. In this study, we evaluated the efficacy of the AT1R antagonist candesartan against bladder cancer. For the study in vitro, human bladder cancer cells (KU-19-19) were cultured with and without angiotensin II (A II) and candesartan, and cell viability and vascular endothelial growth factor (VEGF) secretion were analyzed. Also for the study in vivo, a tumor xenograft model was prepared in nude mice using KU-19-19 cells. Mice were administered candesartan daily by oral gavage, and paclitaxel via intravenous infusion. Microvessel density, VEGF expression, and apoptosis were investigated. Candesartan did not induce direct toxicity in KU-19-19 cells, but VEGF was significantly lower in candesartan-treated cells than in the A II-treated control cells. In mice, candesartan, paclitaxel and candesartan-paclitaxel significantly suppressed tumor growth to 46.0%, 35.8% and 17.3%, respectively, of the tumor volume in the control group, showing that combined treatment significantly inhibited tumor growth compared to the candesartan group. Microvessel density and VEGF were significantly decreased in the candesartan and candesartan-paclitaxel groups compared to the control group. The apoptotic index was significantly increased in the paclitaxel and candesartan-paclitaxel groups compared to the control and candesartan groups. In our experimental model, candesartan prevented bladder cancer growth by inhibiting angiogenesis. Furthermore, combined treatment with candesartan and paclitaxel enhanced paclitaxel-induced cytotoxicity. These results suggest that the AT1R antagonist candesartan may be a candidate for innovative therapy for bladder cancer.     

Angiotensin II acts through the angiotensin 1a receptor to upregulate pendrin

Pendrin is an anion exchanger expressed in the apical regions of B and non-A, non-B intercalated cells. Since angiotensin II increases pendrin-mediated Cl(-) absorption in vitro, we asked whether angiotensin II increases pendrin expression in vivo and whether angiotensin-induced hypertension is pendrin dependent. While blood pressure was similar in pendrin null and wild-type mice under basal conditions, following 2 wk of angiotensin II administration blood pressure was 31 mmHg lower in pendrin null than in wild-type mice. Thus pendrin null mice have a blunted pressor response to angiotensin II. Further experiments explored the effect of angiotensin on pendrin expression. Angiotensin II administration shifted pendrin label from the subapical space to the apical plasma membrane, independent of aldosterone. To explore the role of the angiotensin receptors in this response, pendrin abundance and subcellular distribution were examined in wild-type, angiotensin type 1a (Agtr1a) and type 2 receptor (Agtr2) null mice given 7 days of a NaCl-restricted diet (< 0.02% NaCl). Some mice received an Agtr1 inhibitor (candesartan) or vehicle. Both Agtr1a gene ablation and Agtr1 inhibitors shifted pendrin label from the apical plasma membrane to the subapical space, independent of the Agtr2 or nitric oxide (NO). However, Agtr1 ablation reduced pendrin protein abundance through the Agtr2 and NO. Thus angiotensin II-induced hypertension is pendrin dependent. Angiotensin II acts through the Agtr1a to shift pendrin from the subapical space to the apical plasma membrane. This Agtr1 action may be blunted by the Agtr2, which acts through NO to reduce pendrin protein abundance.     

Angiotensin II induces oxidative stress in prostate cancer

Angiotensin II has been shown to be a cytokine especially acting as a growth factor. A local renin-angiotensin system has been identified in the prostate gland, and the physiologic function of angiotensin II seems to be similar in prostate cancer, as we previously reported. In the present study, we explored the biological role of angiotensin II in oxidative stress of prostate cancer cells. Activated Akt was determined, and the expression of oxidative stress-related proteins (p47phox, manganese superoxide dismutase 2, glutathione peroxidase) was examined by Western blotting in LNCaP cells, which were stimulated with angiotensin II and/or an angiotensin II receptor type 1 blocker, candesartan. To examine DNA damage induced by angiotensin II, 8-hydroxy-2'-deoxyguanosine was determined, and Western blots were analyzed to detect checkpoint proteins including p53, Chk2, and cdc2. Immunocytochemical studies of inducible nitric oxide synthase and superoxide anion radical (O(2)(-)) were done in LNCaP cells stimulated with angiotensin II. The phosphorylation of Akt was induced by angiotensin II treatment and inhibited by candesartan, as well as by LY294002, an inhibitor of phosphoinositide 3-kinase. Oxidative stress-related proteins were up-regulated by angiotensin II and inhibited by pretreatment with candesartan or catalase. The level of 8-hydroxy-2'-deoxyguanosine was increased by angiotensin II and conversely decreased by candesartan. Immunocytochemical studies showed that angiotensin II enhanced an inflammatory marker, inducible nitric oxide synthase, and the production of O(2)(-) radical. The hypothesis that angiotensin II has the potential to induce oxidative stress, which may be implicated in carcinogenesis of the prostate gland through long-term exposure to chronic inflammation is proposed.     

Effects of angiotensin-II receptor blocker candesartan cilexetil in rats with dilated cardiomyopathy

We examined effects of an angiotensin-II receptor blockers, candesartan cilexetil, in rats with dilated cardiomyopathy after autoimmune myocarditis. Candesartan cilexetil showed angiotensin-II blocking action in a dose-dependent manner in rats with dilated cardiomyopathy. Twenty-eight days after immunization, surviving Lewis rats were divided into four groups and given candesartan cilexetil at 0.05 mg/kg, 0.5 mg/kg or 5 mg/kg per day (Group-C0.05, n = 15, Group-C0.5, n = 15 and Group-C5, n = 15, respectively) or vehicle alone (Group-V, n = 15). After oral administration for 1 month, the left ventricular end-diastolic pressure and heart weight/body weight ratio were lower in Group-C0.05 (13.3± 1.1 mmHg and 3.7± 0.2 g/kg, respectively), in Group-C0.5 (8.0± 0.9 mmHg and 3.3± 0.1 g/kg, respectively) and in Group-C5 (5.5± 1 mmHg and 3.1± 0.1 g/kg, respectively) than in Group-V (13.5± 1.0 mmHg and 3.8± 0.2 g/kg, respectively). The area of myocardial fibrosis was also lower in Group-C0.05 (25± 3%), in Group-C0.5 (20± 3%), and in Group-C5 (12± 1%) than in Group-V (32± 4%). Furthermore, expressions of transforming growth factor-1 and collagen-III mRNA were suppressed in Group-C0.05 (349± 23% and 395± 22%, respectively), Group-C0.5 (292± 81% and 364± 42%, respectively) and in Group-C5 (204± 63% and 259± 33%, respectively) compared with those in Group-V (367± 26% and 437± 18%, respectively). These results suggest that candesartan cilexetil can improve the function of inefficient heart. (Mol Cell Biochem 269: 137–142, 2005)     

Attenuation of heart failure due to coronary stenosis by ACE inhibitor and angiotensin receptor blocker

It is not known how the angiotensin-converting enzyme (ACE) inhibitor and angiotensin II receptor blocker (ARB) attenuate heart failure (HF) in viable ischemic hearts. To assess HF in a rat coronary stenosis (CS) model, we administered vehicle and quinapril or candesartan (or both) orally for 12 wk. Compared with the sham group, the vehicle group showed impaired myocardial perfusion, impaired coronary endothelial nitric oxide (NO) function in vitro, exhausted myocardial mitochondrial respiration, larger left ventricular (LV) dimensions and lower ejection fraction, lower LV rate of pressure development over time (dP/dt), lower slopes of LV end-systolic pressure-dimension relations (ESPDRs), and increased myocardial fibrosis. Treatment with quinapril or candesartan ameliorated these parameters without modifying the epicardial CS severity. Moreover, their combination maintained similar myocardial perfusion, despite a trend toward lower blood pressure, and showed distinctive neurohumoral modulation, normalized mitochondrial respiration, and increased ESPDR slopes. Thus improved myocardial blood flow and coronary flow reserve by quinapril or candesartan are the key to alleviate CS-induced HF, and their combination may have a therapeutic significance partly through ameliorated mitochondrial respiration and improved LV systolic function.     

Effects of inhibitors of the renin-angiotensin system on reducing blood pressure and expression of inflammatory factors in CHD patients: A network meta-analysis

The renin-angiotensin system (RAS) is an ever-evolving endocrine system with considerable checks and balances on the production and catabolism of angiotensin peptides most likely due to the manifold effects of angiotensins. We aimed to explore the effects of different inhibitors of RAS on blood pressure and expression of inflammatory factors in patients with coronary heart disease (CHD). We initially searched PubMed, EMBASE and Cochrane Library electronic databases with nine eligible randomized controlled trials enrolled. Direct and indirect evidence was combined to calculate the weighted mean difference value and draw surface under the cumulative ranking curves. The results demonstrated that, compared with placebo and enalapril, ramipril had a better effect on reducing systolic blood pressure after short-term usage of drugs (<12 months), while perindopril had better effects on reducing diastolic blood pressure and C-reactive protein expression. Furthermore, after long-term usage of drugs (≥12 months), there was no significant difference among olmesartan, quinapril and candesartan in the treatment of patients with CHD. Perindopril and ramipril had better effects on inhibiting blood pressure and expression of inflammatory factors among eight inhibitors after short-term usage of drugs (<12 months); while quinapril had better effects on reducing blood pressure and expression of inflammatory factor after long-term usage of drugs, and there was little difference in the effects between olmesartan and candesartan (≥12 months). Perindopril may have better short-term effects on reducing blood pressure and expression of inflammatory factor, while quinapril may have better long-term effects on reducing blood pressure and expression of inflammatory factor.